A cloud of ash belches out of Mexico's Popocatepetl volcano, some near Mexico City, as seen from Paso de Cortes, in the Mexican central state of Puebla. Authorities have raised the alert level to "Yellow Phase Three," the fifth of a seven-stage warning system, restricting access to an area of 12 km around the volcano while preparing evacuation routes and shelters. less

A cloud of ash belches out of Mexico's Popocatepetl volcano, some near Mexico City, as seen from Paso de Cortes, in the Mexican central state of Puebla. Authorities have raised the alert level to "Yellow Phase ... more

Photo: AFP, AFP/Getty Images

A cloud of ash belches out of Mexico's Popocatepetl volcano,... Photo-4661791.62910 - NewsTimes

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A man walks with a horse and a dog next to signs reading "Evacuation route" in Santiago Xalitzintla community, near the Popocatepetl volcano, Puebla state, 55 km southeast of Mexico City, on May 19, 2013. The National Disaster Prevention Centre (CENAPRED) raised the alert level to "yellow phase three." less

A man walks with a horse and a dog next to signs reading "Evacuation route" in Santiago Xalitzintla community, near the Popocatepetl volcano, Puebla state, 55 km southeast of Mexico City, on May 19, 2013. The ... more

Photo: AFP, AFP/Getty Images

A man walks with a horse and a dog next to signs reading... Photo-4661790.62910 - NewsTimes

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A cloud of ash belches out of Mexico's Popocatepetl volcano, some 55 km from Mexico City, as seen from Cholula, in the Mexican central state of Puebla, on May 15, 2013. The volcano spewed a new column of ash late Tuesday, with some of the material falling on three towns while glowing rocks landed on the towering mountain's slope. Authorities have raised the alert level to "Yellow Phase Three," the fifth of a seven-stage warning system, restricting access to an area of 12 km around the volcano while preparing evacuation routes and shelters. less

A cloud of ash belches out of Mexico's Popocatepetl volcano, some 55 km from Mexico City, as seen from Cholula, in the Mexican central state of Puebla, on May 15, 2013. The volcano spewed a new column of ash ... more

Photo: AFP, AFP/Getty Images

A cloud of ash belches out of Mexico's Popocatepetl volcano,... Photo-4661784.62910 - NewsTimes

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A cloud of ash belches out of Mexico's Popocatepetl volcano, some 55 km from Mexico City, as seen from Cholula, in the Mexican central state of Puebla, on May 15, 2013. The volcano spewed a new column of ash late Tuesday, with some of the material falling on three towns while glowing rocks landed on the towering mountain's slope. Authorities have raised the alert level to "Yellow Phase Three," the fifth of a seven-stage warning system, restricting access to an area of 12 km around the volcano while preparing evacuation routes and shelters. less

A cloud of ash belches out of Mexico's Popocatepetl volcano, some 55 km from Mexico City, as seen from Cholula, in the Mexican central state of Puebla, on May 15, 2013. The volcano spewed a new column of ash ... more

Photo: AFP, AFP/Getty Images

A cloud of ash belches out of Mexico's Popocatepetl volcano,... Photo-4661785.62910 - NewsTimes

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Taboola Gallery Frame Item-85307.62910 - NewsTimes

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Clouds of ash and smoke are spewed from the Popocatepetl Volcano as seen from Santiago Xalitxintla, in Puebla, Mexico, on May 13, 2013. According to a report by the National Center of Prevention of Disasters (CENAPRED) the yellow alert phase three is still in force. less

Clouds of ash and smoke are spewed from the Popocatepetl Volcano as seen from Santiago Xalitxintla, in Puebla, Mexico, on May 13, 2013. According to a report by the National Center of Prevention of Disasters ... more

Photo: RONALDO SCHEMIDT, AFP/Getty Images

Clouds of ash and smoke are spewed from the Popocatepetl Volcano as... Photo-4661779.62910 - NewsTimes

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The Popocatepetl Volcano, Mexico's second highest peak just 55 km southeast of Mexico City, is seen from Santiago Xalitxintla, in Puebla, on May 14, 2013 spewing a cloud of ash and smoke. The National Disaster Prevention Centre (CENAPRED) raised the alert level on Sunday to "yellow phase three." less

The Popocatepetl Volcano, Mexico's second highest peak just 55 km southeast of Mexico City, is seen from Santiago Xalitxintla, in Puebla, on May 14, 2013 spewing a cloud of ash and smoke. The National Disaster ... more

A man sweeps the street at Santiago Xalitzintla community in Puebla state, near the Popocatepetl Volcano, Mexico's second highest peak, just 55 km southeast of Mexico City, on May 19, 2013. The National Disaster Prevention Centre (CENAPRED) raised the alert level to "yellow phase three". The sign reads: "Evacuation route." less

A man sweeps the street at Santiago Xalitzintla community in Puebla state, near the Popocatepetl Volcano, Mexico's second highest peak, just 55 km southeast of Mexico City, on May 19, 2013. The National ... more

Photo: AFP, AFP/Getty Images

A man sweeps the street at Santiago Xalitzintla community in Puebla... Photo-4661787.62910 - NewsTimes

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Two members of the Federal Police talk with the Popocatepetl volcano in the background in Paso de Cortez, at the Popocatepetl-IztaccÌhuatl National Park, Puebla state, 55 km southeast of Mexico City, on May 19, 2013. The National Disaster Prevention Centre (CENAPRED) raised the alert level to "yellow phase three." less

Two members of the Federal Police talk with the Popocatepetl volcano in the background in Paso de Cortez, at the Popocatepetl-IztaccÌhuatl National Park, Puebla state, 55 km southeast of Mexico City, on May ... more

Photo: AFP, AFP/Getty Images

Two members of the Federal Police talk with the Popocatepetl... Photo-4661789.62910 - NewsTimes

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Taboola Gallery Frame Item-85307.62910 - NewsTimes

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A peasant is seen working as Popocatepetl Volcano, Mexico's second highest peak, just 55 kms southeast of Mexico City, is seen from Santiago Xalitxintla, in Puebla, on May 18, 2013 spewing a cloud of ash and smoke. The National Disaster Prevention Centre (CENAPRED) raised the alert level to "yellow phase three." less

A peasant is seen working as Popocatepetl Volcano, Mexico's second highest peak, just 55 kms southeast of Mexico City, is seen from Santiago Xalitxintla, in Puebla, on May 18, 2013 spewing a cloud of ash and ... more

Photo: AFP, AFP/Getty Images

A peasant is seen working as Popocatepetl Volcano, Mexico's... Photo-4661786.62910 - NewsTimes

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Backdropped by Popocatepetl Volcano, Mexico's second highest peak just 55 km southeast of Mexico City, a man rides his bicycle in San Nicolas de los Ranchos, in the state of Puebla, on May 14, 2013. The National Disaster Prevention Centre (CENAPRED) raised the alert level on Sunday to "yellow phase three" as the Popocatepetl continues to spew ash and smoke. less

Backdropped by Popocatepetl Volcano, Mexico's second highest peak just 55 km southeast of Mexico City, a man rides his bicycle in San Nicolas de los Ranchos, in the state of Puebla, on May 14, 2013. The ... more